Pre motor neurons in the oculomotor systems will be studied with intra and extracellular recording techniques in anesthesized cats and monkeys. Neurons will be identified electrophysiologically by their antidromic invasion from central stimulating sites and patterns of orthodromic excitation and inhibition will be studied. Selected neurons will be stained intracellularly with horseradish peroxidase (HRP) and after appropriate histological procedures axonal and dendritic trees reconstructed with a camera lucida technique. Further, pathways will be defined by extracellular iontophoresis of HRP and radioactive amino acids into electrophysiologically identified sites followed by histological reconstruction of the locations of labeled neuronal somas and terminals. When necessary extracellular iontophoretic experiments will be performed in animals with selected brainstem lesions. Lastly, extracellular recording of antidromically identified oculomotor interneurons will be performed in the alert cat and discharge frequencies correlated with eye movements.